The present invention relates generally to spline connections wherein a splined male member, such as a splined shaft, is engaged with a splined female member, for example, a hub or gear wheel having a splined central bore. More particularly, the invention relates to anti-backlash mechanisms for such spline connections.
The suppression or avoidance of backlash is an essential consideration in the design of mechanical linkages having spline connections. Backlash, or play in the spline connection, results in deterioration of the splines in any spline connection that is subjected to substantial mechanical loads. Such deterioration typically accelerates as the amount of backlash in the spline connection increases.
Backlash poses another type of problem in mechanical control linkages that are under automatic feedback control. Such linkages are used, for example, in airfoil control systems in airplanes. The presence of backlash in spline connections in such linkages results in an unstable feedback condition that causes uncontrolled "hunting" of the system.
Without some type of anti-backlash mechanism, a spline connection normally has some backlash, even under close tolerance conditions. In applications where the purpose of the spline connection is to accommodate relative axial sliding motion between the connected members, some backlash is virtually unavoidable if there is to be provided sufficient radial clearance to allow free axial sliding between the members. However, even in other applications where relative axial sliding need not be accommodated and there is merely sought a tight, torque-transmitting connection that can be readily disassembled and reassembled, backlash is a problem because at least some minimal radial clearance must be provided between the splined male and female members in order to allow for their initial assembly and subsequent disassembly. It is to the latter applications that the present invention is directed.
In one type of previously known anti-backlash mechanism, a shaft having splines at one end is provided with a relatively large diameter axial bore extending inwardly from the splined end of the shaft, such that the splined portion of the shaft is essentially tubular in configuration. The splined tubular portion of the shaft is further provided with several longitudinal slots passing through the tubular wall of the shaft and extending along the splined portion of the shaft. The slots divide the tubular end of the shaft into a set of deflectable, splined fingers. The splined portion of the shaft, including the deflectable fingers, is inserted into a splined female member and a tapered plug is driven into the bore of the tubular shaft from the opposite side of the female member. The plug drives the splined fingers radially outwardly to securely engage the splines of the female member.
There are several disadvantages to the above-described prior art mechanism, however. For example, the splined fingers are necessarily somewhat flexible and thereby introduce some torsional flexibility into the splined shaft. Thus, although spline backlash is eliminated, a similar problem of torsional flexibility is introduced. This torsional flexibility is aggravated by the fact that it is primarily only the ends of the fingers of the splined shaft, which are in direct contact with the tapered plug, that are driven outwardly to securely engage the splines of the female member, leaving the backlash unrestricted along most of the length of the splined shaft. Another disadvantage is that the mechanism can only be employed in situations where there is sufficient access to the end of the splined shaft to permit the plug to be manually inserted and seated. Further, subsequent disassembly of the spline connection by removal of the tapered plug is relatively difficult.
In another previous approach to the problem of backlash, the splined shaft is tapered such that it can be driven axially into a splined female member that is cooperably tapered to receive the splined shaft. In a related prior art approach, a standard tapered key is driven into a keyway between the splined members to bind them together. With each of these two approaches, however, subsequent disassembly of the parts is difficult, particularly where servicing and maintenance must be carried out in the field in the absence of machine shop facilities.
Accordingly, it is the general object and purpose of the present invention to provide a mechanism for eliminating backlash in a spline connection.
It is also an object of the present invention to provide a mechanism for locking cooperably splined male and female members together with no backlash between them.
It is another object of the present invention to provide a mechanism that eliminates backlash between splined members and which also allows ready disassembly and reassembly of the splined members, particularly in the field and without necessity of special tools or facilities.
It is yet another object of the present invention to provide an anti-backlash mechanism that takes up no additional space beyond that ordinarily occupied by a conventional spline connection. It is another object to provide such an anti-backlash mechanism that is simple and reliable in design and operation.